content: package ciscoroutertool.settings;
  
  /* 
   * Password Hashing With PBKDF2 (http://crackstation.net/hashing-security.htm).
   * Copyright (c) 2013, Taylor Hornby
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without 
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, 
   * this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   * this list of conditions and the following disclaimer in the documentation 
   * and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
   * POSSIBILITY OF SUCH DAMAGE.
   */
  
  import java.security.SecureRandom;
  import javax.crypto.spec.PBEKeySpec;
  import javax.crypto.SecretKeyFactory;
  import java.math.BigInteger;
  import java.security.NoSuchAlgorithmException;
  import java.security.spec.InvalidKeySpecException;
  
  /*
   * PBKDF2 salted password hashing.
   * Author: havoc AT defuse.ca
   * www: http://crackstation.net/hashing-security.htm
   */
  public class PasswordHash {
      public static final String PBKDF2_ALGORITHM = "PBKDF2WithHmacSHA1";
  
      // The following constants may be changed without breaking existing hashes.
      public static final int SALT_BYTE_SIZE = 24;
      public static final int HASH_BYTE_SIZE = 24;
      public static final int PBKDF2_ITERATIONS = 1000;
  
      public static final int ITERATION_INDEX = 0;
      public static final int SALT_INDEX = 1;
      public static final int PBKDF2_INDEX = 2;
  
      /**
       * Returns a salted PBKDF2 hash of the password.
       *
       * @param   password    the password to hash
       * @return              a salted PBKDF2 hash of the password
       */
      public static String createHash(String password)
          throws NoSuchAlgorithmException, InvalidKeySpecException
      {
          return createHash(password.toCharArray());
      }
  
      /**
       * Returns a salted PBKDF2 hash of the password.
       *
       * @param   password    the password to hash
       * @return              a salted PBKDF2 hash of the password
       */
      public static String createHash(char[] password)
          throws NoSuchAlgorithmException, InvalidKeySpecException
      {
          // Generate a random salt
          SecureRandom random = new SecureRandom();
          byte[] salt = new byte[SALT_BYTE_SIZE];
          random.nextBytes(salt);
  
          // Hash the password
          byte[] hash = pbkdf2(password, salt, PBKDF2_ITERATIONS, HASH_BYTE_SIZE);
          // format iterations:salt:hash
          return PBKDF2_ITERATIONS + ":" + toHex(salt) + ":" +  toHex(hash);
      }
  
      /**
       * Validates a password using a hash.
       *
       * @param   password        the password to check
       * @param   correctHash     the hash of the valid password
       * @return                  true if the password is correct, false if not
       */
      public static boolean validatePassword(String password, String correctHash)
          throws NoSuchAlgorithmException, InvalidKeySpecException
      {
          return validatePassword(password.toCharArray(), correctHash);
      }
  
      /**
       * Validates a password using a hash.
       *
       * @param   password        the password to check
       * @param   correctHash     the hash of the valid password
       * @return                  true if the password is correct, false if not
       */
      public static boolean validatePassword(char[] password, String correctHash)
          throws NoSuchAlgorithmException, InvalidKeySpecException
      {
          // Decode the hash into its parameters
          String[] params = correctHash.split(":");
          int iterations = Integer.parseInt(params[ITERATION_INDEX]);
          byte[] salt = fromHex(params[SALT_INDEX]);
          byte[] hash = fromHex(params[PBKDF2_INDEX]);
          // Compute the hash of the provided password, using the same salt, 
          // iteration count, and hash length
          byte[] testHash = pbkdf2(password, salt, iterations, hash.length);
          // Compare the hashes in constant time. The password is correct if
          // both hashes match.
          return slowEquals(hash, testHash);
      }
  
      /**
       * Compares two byte arrays in length-constant time. This comparison method
       * is used so that password hashes cannot be extracted from an on-line 
       * system using a timing attack and then attacked off-line.
       * 
       * @param   a       the first byte array
       * @param   b       the second byte array 
       * @return          true if both byte arrays are the same, false if not
       */
      private static boolean slowEquals(byte[] a, byte[] b)
      {
          int diff = a.length ^ b.length;
          for(int i = 0; i < a.length && i < b.length; i++)
              diff |= a[i] ^ b[i];
          return diff == 0;
      }
  
      /**
       *  Computes the PBKDF2 hash of a password.
       *
       * @param   password    the password to hash.
       * @param   salt        the salt
       * @param   iterations  the iteration count (slowness factor)
       * @param   bytes       the length of the hash to compute in bytes
       * @return              the PBDKF2 hash of the password
       */
      private static byte[] pbkdf2(char[] password, byte[] salt, int iterations, int bytes)
          throws NoSuchAlgorithmException, InvalidKeySpecException
      {
          PBEKeySpec spec = new PBEKeySpec(password, salt, iterations, bytes * 8);
          SecretKeyFactory skf = SecretKeyFactory.getInstance(PBKDF2_ALGORITHM);
          return skf.generateSecret(spec).getEncoded();
      }
  
      /**
       * Converts a string of hexadecimal characters into a byte array.
       *
       * @param   hex         the hex string
       * @return              the hex string decoded into a byte array
       */
      private static byte[] fromHex(String hex)
      {
          byte[] binary = new byte[hex.length() / 2];
          for(int i = 0; i < binary.length; i++)
          {
              binary[i] = (byte)Integer.parseInt(hex.substring(2*i, 2*i+2), 16);
          }
          return binary;
      }
  
      /**
       * Converts a byte array into a hexadecimal string.
       *
       * @param   array       the byte array to convert
       * @return              a length*2 character string encoding the byte array
       */
      private static String toHex(byte[] array)
      {
          BigInteger bi = new BigInteger(1, array);
          String hex = bi.toString(16);
          int paddingLength = (array.length * 2) - hex.length();
          if(paddingLength > 0)
              return String.format("%0" + paddingLength + "d", 0) + hex;
          else
              return hex;
      }
  }